THE $D^{1}\Pi \to X^{1}\Sigma$ BAND OF NaK REVISITED

Abstract

Several recent papers have been published using the spectroscopic constants of the $X^{1} \Sigma$ and $D^{1} \Pi$ states of $Na^{39}k$ as determined by $Toueg^{1}$ These constants are incorrect since the rotational quantum numbers for 11 of the 12 fluorescence series were misassigned. Toueg failed to recognize that there were significant perturbations in many of the $D^{1} \Pi$ levels that were excited by the Argon ion laser lines. We have remeasured and analyzed the spectroscopic plates of Toueg and have assigned quantum numbers to 36 $Na^{39}K$ and $6 Na^{41} K$ fluorescence aeries excited by six different Argon ton laser lines. About 2600 directly excited and also collisionally transferred lines have been used to obtain the ground state Dunham constants and upper state term values. A Least squares fit of these data gives an rms of $0.024\, cm^{-1}$ for a range of $v^{\prime} = 1$ to $23, v^{\prime\prime} = 0$ to 24 and J$ = 4$ to 122. Perturbations as large as $1.5\, cm^{-1}$ have been observed in the $D^{1}\Pi$ state. The potential curves and the results of our analysis will be presented.